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PATENTED 00116, 1906. H. B. HOLMES & E. B; ORAIT. SPRING JACK FOR TELEPHONE SWITGHBQARDS.'

APPLIGATION IILBD JUNE 24,1905.

2 SHEETS-SHEET 1.

@w #3 ma Z i E I PATENTED OCT. 16, 1906. H. B. HOLMES & B. B. CRAFT.

SPRING JACK FOR TELEPHONE SWITOHBOARDS.

' APPLICATION FILED JUNE 24. 1905.

2 SHEETSSHEET 2.

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UNITED STATES PATENT OFFICE.

HOWARD B. HOLMES, OF PARK RIDGE, AND EDWARD B. CRAFT, OF CHICAGO, ILLINOIS, ASSIGNORS TO WESTERN ELECTRIC COMPANY, v OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

SPRING-JACK FOR TELEPHONE-SWITOHBOARDS.

Specification of Letters Patent.

Patented Oct. 16, 1906.

Application filed June 24:, 1905. Serial No. 266,740.

To aLZ whmn it may concern:

Be it known that we, HOWARD B. HOLMES, residing at Park Ridge, and EDWARD B. CRAFT, residing at Chicago, in the county of Cook and State of Illinois, citizens of the United States, have invented a certain new and useful Improvement in Spring-Jacks for Telephone-Switchboards, of which the following is a full, clear, concise, and exact description.

Our invention relates to spring jack switches for telephone-switchboards.

The first form employed was known as the jack-knife switch, which is illustrated in Letters Patent No. 293,198, of February 5, 1884, to Charles E. Scribner, application filed August 23, 1879. The jack-knife switch was modified to occupy less space upon the switchboard by James C. Warner, as shown in Patent No. 321,553, July 7, 1885. (See also Figure 1 of Patent No. 305,021.) Since about the date of the patent to Richard V. Freeman, No. 309,218, December 16,1884, it has been common to build up the jacks in strips, usually of twenty, the frame being of rubber and the jacks being on half-inch centers. Certain defects or limitations have been found in the use of these jacks which our invention is designed to remedy. In such jacks it is customary to mount the springs of a row in a common strip, said springs being disposed on edge, with suitable interleaving insulating-strips in milled slots provided in said strip. The entire row of springs is usually held in place by a common clampingstrip secured by suitable screws.

Our invention particularly applies to that class known as cut-off jacks, where one or more switch-contacts are required in addition to the regular line-springs. In such jacks it is of the utmost importance that the assembled springs of a single jack be rigidly clamped together in order .to maintain a positive contact between the local switchingsprings above noted.

In the earlier forms of jacks before described it is exceedingly difficult to produce commercially the rigid clamping effect desired. A great deal of this trouble is due to the manufacturers inability to obtain sheet metal and insulating material for the springs and insulators which is uniform in thickness.

This uniformity is necessary in order that the springs may always be tightly wedged in their respective mounting-slots. This trouble is further aggravated by the fact that the ordinary insulating material from which these mounting-strips are usually made, such as hard rubber, is very liable to warp and shrink with age, causing a distortion which tends to change, and oftentimes destroy, the tension between springs. It will also be noted that in constructions of this sort in order to remove a defective jack or spring for repairs it is necessary to practically disassemble the entire strip, inasmuch as all the jacks are dependent upon a single retainingstrip. This fact tends to increase to a considerable extent the cost of such repairs.

Our invention consists in assembling the springs of several jacks in units and arranging them so that each unit may be readily removed from the bank of jacks to which it belongs. These said units consist of rigid frames, preferably L-shaped, in which the line and contact springs, with their interleaving insulators, are disposed on edge or in a vertical plane, the same being rigidly clamped in said frame by screws assing through the springs into a clamping-p ate opposite the vertical side of the frame. The contact-surfaces of the jacks are thus disposed on edge to avoid accumulations of dust thereon, at the same time providing for a practical arrangement of parts, which are securely clamped together, producing a posi tive tension between contacts irrespectiveof slight variations in the thickness of various parts. The units thus formed lend themselves very nicely to economical manufacture, inasmuch as they may be made up and carried in stock in large quantities, to be assembled in groups on suitable mounting-plates, as required, the unit itself being in the majority of cases standard, whereas the mountingplates may vary considerably as to number per strip and centers on which the jacks are mounted.

The mounting-plate consists of a metal strip on one side of which is mounted a facestrip, of rubber or other suitable material, in which are located the test-.thimbles, which in turn have rearwardlyprojecting strips adapted to rest in insulated slots in the jack units, the ends projecting through the units to serve as terminals. Back of the face-strip suitable mounting-holes are provided in the metal plate to secure the jack units in" aline ment with the test-thimbles.

Our invention will be more readily understood by reference to the accompanying drawings, in which i I Fig. l is a plan view of a section of a strip of jack units embodying our invention. Fig. 2 is a sectional view of a strip through line 2 2 of Fig. 1, with portions of the springs broken away. Fig. 3 is a front elevation showing the openings adapted to receive the plugs. Fig. 4 is a sectional perspective view of a mounting-strip and the jack unit removed and also shows a test-thimble with rearwardly-projecting terminal. Fig. 5 is an isometric view showing the several parts of a' j aok. unit ready for assembly. Fig. 6 shows an enlargedsectional view of the jack unit through one of the clamping-screws, and Fig. 7 is an enlarged detail view of the insulating-button and its mounting.

The same parts are indicated by similar letters of reference throughout the several figures of the drawings.

As illustrated, the strip of jacks comprises a metalmounting-plate a, an insulating facestrip 6, with test-sleeves rigidly mounted therein and jack units mounted on said metal strip with the 1ine-springs disposed immediately behind the holes of the testthimbles c in position to engage the contacts of a plug when inserted. Each of the springjacks illustrated comprises a test-thimble c anda unit composed of the usual line-springs d e and cut-oif contacts f g. The test-thimble is provided with a connecting strip or tongue h, extending through the channel '5, provided in the insulating-strip k. The test thimble or sleeve, with its connecting-strip, may be conveniently formed up from a single unching, the sleeve 0 beingdrawn to shape from the flat strip.

The jack unit or removable portion comprises the metal frame I, the corresponding clamping-plate or jaw m, and the line-springs d e, the respective corresponding cut-off contacts f g, and the strips of insulating material, all secured together, as shown, by clamping-screws n.

The projecting portion of the frame is bent up, as indicated at o, to carry an insulatingbutton 19. The spring 6 is adapted to rest against theface p of the insulating-button with the desired amount of tension. The cut-off spring-contact g, as shown in Fig. 5, is provided with an opening adapted to fit the projecting end p of said insulating-button. It will be understood that the stud or insulating-piece carried on the line-spring d is normally pressed by the tension of said spring against the cut-off contact-spring f to cause which are clamped together, as illustrated in Figs. 5 and 6, a unit, since these parts are built up separately and clamped together and,

adapted to be united by the thimble or test portion by simply slipping the same onto the spring h, which projects rearwardly from the thimble, as most clearly illustrated in Fig. 4. Thus we have realized means for clamping the springs of each individual jack, so that there will be no possibility of trouble from loss of tension, a compact assembly of the jacks in a strip, and ease in removing individual jacks for repairs without disturbing the remainder of the strip. It will be understood that jacks of standard size may be supplied for use with frames or mountingstrips difiering in thickness, length, and capacity.

Having thus described our invention, we claim 1. A strip of spring-jacks for telephone switchboards comprising a mounting-plate, an insulating face-strip supported thereby,

and provided with test-rings for the j acks, the

said rings being provided each with an extension integral therewith, in combination with jack units containing line and contact springs mounted upon said plate, said jack units being each provided with an opening or space through which the extension of its corresponding testring is adapted to be inserted and maintained insulated.

2. A jack unit having line and contact springs disposed on edge, insulatin -strips between the same, the U-shaped meta frame comprising an L-shaped supporting member and a jaw m all rigidly secured together, substantially as and for the purpose specified.

3. In a strip of spring-jacks, the combina tion with a mounting-plate, of a face-strip attached thereto, test-thimbles mounted in said face-strip ;and each provided with a rearward extension integral therewith, and jack units each provided with an opening or space through which the extension of its corresponding test-thimble is adapted to be inserted and maintained insulated, said jack units being adapted to ,be individually fastened to said mounting-plate or removed therefrom without disturbing adjacent units.

4. The combination with the frame carrying the test-rings and their extensions, of jack units consisting each of line-springs and cut-off springs or contacts, insulated and clamped together, said jack units being each In witness whereof We hereunto subscribe our names this 25th day of May, A. D. 1905. lo

HOWARD B. HOLMES. EDWARD B. CRAFT.

Witnesses:

F. P. McINTosH, E. F. BEAUBIEN. 

